Added page in docs for lunar sim and instructions on how to build and…

… run it (issue space-ros/demos#50)

source/Demos.rst

@@ -5,6 +5,7 @@ There are currently two Space ROS demonstration applications.
 The first demo uses `MoveIt2 <https://moveit.ros.org/>`_ and a model of the `Canadarm manipulator <https://en.wikipedia.org/wiki/Canadarm>`_ along with the Space ROS base image.
 In this demo, MoveIt2 is used to plan the motion for the Canadarm, which is running in simulation.
 The second demo shows the `Mars Curiosity rover <https://mars.nasa.gov/msl/home/>`_ in simulation, presenting multiple ROS 2 services to allow the user to directly control the rover.
+The third demo is a lunar world simulation with realistic terrain and lighting as well as an open-source lunar rover model.
 The following pages go into detail to show you how to run these demo applications.
 
  .. toctree::
@@ -13,3 +14,4 @@ The following pages go into detail to show you how to run these demo application
 
    Demos/Canadarm
    Demos/Mars-Rover
+   Demos/LunarSim

source/Demos/LunarSim.rst

@@ -0,0 +1,45 @@
+Lunar Sim Demo
+==============
+
+Space ROS Lunar Sim Demo Docker Image
+-------------------------------------
+
+The Space ROS Lunar Sim Demo docker image uses the spaceros docker image (*osrf/space-ros:latest*) as its base image.
+The Dockerfile installs all of the prerequisite system dependencies along with the demo source code, then builds the Space ROS Lunar Sim Demo.
+
+This demo includes a Gazebo simulation of the lunar environment (specfically around the Shackleton crater near the south pole). It uses
+Digital Elevation Models (DEMs) from the Lunar Orbiter Laser Altimeter (LOLA) to accurately simulate the lunar surface in a specific region. It also contains a dynamic model of the Sun that moves according to Ephemeris data.  
+
+Building the Demo Docker
+^^^^^^^^^^^^^^^^^^^^^^^^
+
+The demo image builds on top of the spaceros image.
+To build the docker image, first ensure the spaceros base image is available either by `building it locally <https://github.com/space-ros/space-ros>`_ or pulling it.
+
+Then build lunar_sim demo images:
+
+.. code-block:: bash
+
+  cd ../lunar_sim
+  ./build.sh
+
+
+Running the Demo Docker
+^^^^^^^^^^^^^^^^^^^^^^^
+
+Run the following to allow GUI passthrough:
+
+.. code-block:: bash
+
+  xhost +local:docker
+
+
+Then run:
+
+.. code-block:: bash
+
+	./run.sh
+
+
+Depending on the host computer, you might need to remove the ``--gpus all`` flag in ``run.sh``, which uses your GPUs.
+